1. Field of the Invention
The present invention relates to a high-frequency composite unit for use in mobile communication apparatuses such as a cellular phone, and the like, that can handle multiple frequency bands.
2. Description of the Related Art
When the frequency bands of two mobile communication systems, such as a GSM (Global System for Mobile communications) in the 900 MHz band and a DCS (Digital Cellular System) in the 1.8 GHz band, are relatively close to each other, the two mobile communication systems shares an antenna between them. FIG. 10 is a block diagram showing a structure in which an antenna is shared between the conventional types of mobile communications with different frequency bands. In FIG. 10, reference numeral 51 denotes an antenna, reference numeral 52 denotes a duplexer, reference numeral 53 denotes a switch on the GSM side, while reference numeral 54 denotes a switch on the DCS side. A first terminal 53a of the GSM-side switch 53 is connected to the antenna 51 through the duplexer 52, while a second terminal 53b and a third terminal 53c are respectively connected to Txgsm, which is a transmitting circuit of the GSM, and to Rxgsm, which is a receiving circuit of the GSM. In contrast, a first terminal 54a of the DCS-side switch 54 is connected to the antenna 51 through the duplexer 52, while a second terminal 54b and a third terminal 54c are respectively connected to Txdcs, which is-a transmitting circuit of the DCS, and to Rxdcs, which is a receiving circuit of the DCS. In addition, the duplexer 52 performs a division of frequency bands for each of the GSM and the DCS, and the GSM-side switch 53 and the DCS-side switch 54 perform switching between transmission and reception. The arrangement above permits the single antenna 51 to perform reception and transmission in the two mobile communication systems, that is, the GSM and the DCS.
However, in the conventional arrangement sharing an antenna, since the single antenna is connected to the GSM-side switch and the DCS-side switch through the duplexer, and since the transmitting and receiving circuits are connected through these switches, there is a problem of the increased number of components. Thus, this leads to difficulty in miniaturizing a mobile communication device in which the components are mounted.